This application is based upon and claims benefit of priority of Japanese Patent Application No. 2001-311720 filed on Oct. 9, 2001, the content of which is incorporated herein by reference.
1. Field of the Invention
The present invention relates to a meter such as a speedometer for use in an automotive vehicle.
2. Description of Related Art
An example of a meter for use in an automotive vehicle that includes a mechanically extendable pointer is shown in JP-U-5-19918. The pointer used in the meter slidably extends as the pointer rotates from a zero-scale position toward a full-scale position. The pointer is guided by a guiding groove according to its rotation. However, the structure of the meter becomes complex, because the pointer has to include two pieces of pointer needles telescopically connected to each other, and a guiding groove has to be additionally formed on a scale plate.
The present invention has been made in view of the above-mentioned problem, and an object of the present invention is to provide a meter having an illuminated pointer that looks like extending or shrinking at a zero-scale position or at a vicinity of the zero-scale position without providing a complex mechanical structure, thereby enhancing an ornamental effect of the meter.
A meter such as a speedometer for use in an automobile vehicle includes a scale plate having scale positions circularly aligned in a clockwise direction from a zero scale position to a full-scale position and an illuminated pointer driven by a pointer driver under control of an electronic controller. The meter is so structured that the illuminated pointer is observed as if it extends when a key switch is turned on and as if it is shortened when the key switch is turned off. The meter having this effect is realized by the following ways without providing a complex mechanical structure.
The meter is structured so that the pointer rotates counter-clockwise beyond the zero-scale position up to a rest position when a key switch is turned off. A pointer cover for covering a portion of the pointer in a region between the zero-scale position and the rest position is formed on the scale plate. The pointer is illuminated by light-emitting elements such as light-emitting diodes disposed behind the scale plate.
Upon turning on the key switch when the pointer is positioned at the rest position, a full length of the pointer is illuminated by the light-emitting elements. A considerable part of the tip portion of the pointer is covered by the pointer cover at the rest position. The pointer is rotated clockwise from the rest position to the zero-scale position. The covered part of the pointer is gradually shortened as the pointer rotates clockwise, and the pointer is fully exposed when it reaches the zero-scale position. Therefore, the pointer is observed as if it gradually extends in the course of rotation from the rest position to the zero-scale position, thereby giving an ornamental effect to the pointer. On the other hand, when the pointer rotates counter-clockwise from the zero-scale position to the rest position upon turning off the key switch, the pointer is observed as if it is gradually shortened.
Alternatively, plural light-emitting elements for illuminating the pointer at the zero-scale position are disposed behind the scale plate. Upon turning on the key switch, the plural light-emitting elements are lit one by one so that the pointer is progressively illuminated from its foot portion toward its tip portion. In this manner, the pointer looks like gradually extending at the zero-scale position.
Alternatively, plural light-emitting diodes are embedded in a transparent pointer needle. The embedded light-emitting diodes are sequentially lit to illuminate the pointer progressively from its foot portion toward its tip portion upon turning on the key switch. When the key switch is turned off, the light-emitting diodes are switched off one by one from the one positioned at the tip of the pointer so that illumination of the pointer progressively disappears from the tip portion of the pointer toward the foot portion. In this manner, the pointer is observed as if it is extended or shortened at its zero-scale position. Each light-emitting diode is connected in series to a Zener diode having a respectively different breakdown voltage, and the breakdown voltage of each Zener diode is set to switch on the light-emitting diodes one by one from the one positioned at the foot of the pointer upon turning on the key switch.
Alternatively, plural light sources are disposed in a pointer base connected to a foot of a pointer needle and are covered by bimetal cover. When the key switch is turned on, all the light sources are switched on, and at the same time the bimetal cover is heated to gradually uncover the light sources thereby to progressively illuminate the pointer needle from its foot portion toward its tip portion. On the other hand, upon turning off the key switch, the bimetal cover is cooled to gradually cover the light sources so that illumination of the pointer progressively disappears from its top portion toward its foot portion.
According to the present invention, the pointer of the meter can be so made that it looks like extending or shrinking when the key switch is turned on or off. An ornamental effect is given to the meter without providing a complex mechanical structure.
Other objects and features of the present invention will become more readily apparent from a better understanding of the preferred embodiments described below with reference to the following drawings.